Variations in delta C-13 values among major plant community types in the Xilin River Basin, Inner Mongolia, China

摘要

The delta C-13 values of 51 plant species selected from eight plant communities along a moisture gradient were measured. Our results showed that all the community types that we investigated are dominated by C-3 species in the Xilin River Basin. Large variations in the average C-13 natural abundance of different communities were detected, and the magnitude of delta C-13 values showed the following trend: typical steppe (- 23.0 parts per thousand)> degraded steppe (- 23.5 parts per thousand)> sand dune (- 25.0 parts per thousand)> restoring degraded steppe (- 25.8 parts per thousand)> meadow steppe (- 26.4 parts per thousand)>= saline meadow (- 26.5 parts per thousand)> swamp meadow (-28.2 parts per thousand). The major determinants of the biomass- weighted d13C values in a given community were the presence or absence of C-4 plants, the intrinsic variation among species and the variation of the same species growing in different habitats with different soil- moisture regimes and disturbance history. These results suggested that different habitats support dominant species with different water- use efficiencies and a trend in the community- level delta C-13 values was observed, as ascribed by the contribution of C-4 plants and/ or the variations among species or the response of water- use efficiency of the same species to different soil moisture conditions.